Patent GB-714253-A (GB)
Title: Improvements in or relating to power-driven vehicles
IPC: F16D65/28
Filed: 1951-04-09
Abstract: 714,253. Change -speed control. INTERNATIONAL HARVESTER CO. April 9, 1951 [April 19, 1950]. No. 8175/51. Class 80 (2) [Also in Group XXXI] Relates to a vehicle steering arrangement (see Group XXXI) in which ground engaging units are each driven through a two speed gear, the driven shaft of which can be braked, the gear and brake being under the control of a single hydraulic control member which can be moved from its high speed position through its low speed position into a braking range. As shown, the invention is applied to an endless track tractor in which the tracks 15, 16 are driven from the engine 13 through a clutch main change speed gear and a shaft 19 which is connected through bevel gearing and the two-speed gears with sprocket driving shafts 17, 18. Each two-speed gears comprises low and high speed brake discs L, H and each shaft carries a brake disc B. The' discs L, H, B are controlled hydraulically by a hand control lever 172 for each unit and a pedal 69 controls hydraulically .and mechanically both brake discs B, the arrangement being such that when the disc L is braked, the low speed drive is engaged, when the disc H is braked the high speed drive is engaged and progressive braking of the disc B causes progressive braking action on the shaft 17 or 18 to stop the track on that side of the tractor. A brake shoe carrying yoke member 32 adjustably carries a ball end 84 of a thrust member whose other end has a ball and socket connection with an arm 76 of a twoarmed lever pivoted at 77 and connected to the piston rod 81 of a hydraulic ram 71. The arm 76 is connected by another ball and socket joint to a thrust rod 98 which is connected to a twoarmed lever 91 to which is connected a similar rod 98<SP>1</SP> leading from the other unit. The lever 91 is connected by an arm 100 and rod 102 to the pedal 69. Another brake shoe carrying yoke member 52 is connected to a captive spring structure which is adapted to engage the high speed of the unit. The yoke member receives a ball end of a strut member 123, whose other end is ball shaped and engages a socket in an arm 126 of a two-armed lever pivoted at 128 and whose other arm 127 is connected to the piston rod 132 of a hydraulic ram 110. The hydraulic rams 71. 110 are supplied from a pressure source comprising a reservoir 152 connected by a conduit 153 and a filter 154 to a pump 155 constantly driven by the engine, the pump discharging through a check valve 156, a conduit 157, a pressure controlling device 158 and a conduit 159 into an accumulator chamber 161 having a spring-urged compression plunger 162. When the chamber 161 is expanded on the pressure attaining a maximum the device 158 operates to return liquid to the reservoir 152. The chamber 161 is connected to the rams 71. 110 through a pressure reduction valve 173, a highspeed brake releasing valve 174, a low-speed brake-engaging valve 175 and a shaft brakeengaging valve 176, the preferred form of the latter being described in Specification 666,029. The valves 173 ... 176 are contained in a casing 171 and controlled by the hand lever 172, which is pivoted at 182 and carries a segment 183 meshing with a segment 184 pivoted at 185 and carrying a cam 187 which engages followers 191, 196 on plungers of the valves 174, 175. The arrangement is such that the high-speed drive is engaged in position H of the lever 172 and the low-speed drive in position L. When the lever 172 enters the range B<SP>1</SP>-B a finger 206 on the cam 187 abuts a head 207 on a' pivoted lever 208 to operate the shaft brake-engaging valve 176 dependent on the degree of movement into the range. The lever 208 is normally urged by a spring 211 into a position in which a pad 212. thereon engages a lever 215 mounted on a rockable shaft. The lever 208 of each unit can be moved to actuate the valve 176 independently of the lever 172 by operation of the pedal 69 through a linkage 221 connected to the lever 215, a similar linkage 221<SP>1</SP> being connected to the other unit, the. linkages being so adjusted to cause opening of the valves 176 prior to the exertion of manual force through the members 98, 98<SP>1</SP>. Specifications 555,407, [Group XXXI], 668,029, 114,315, [both in Group XXXIV], and U.S.A. Specifications 2,468,628, 2,470,209 and 2,496,429 are referred to.